Source : Webster's Revised Unabridged Dictionary (1913)

Heptachord \Hep"ta*chord\, n. [Gr. "epta`xordos seven-stringed;
   "epta` seven + xordh` chord: cf. F. heptacorde. See {Seven},
   and {Chord}.]
   1. (Anc. Mus.)
      (a) A system of seven sounds.
      (b) A lyre with seven chords.

   2. (Anc. Poet.) A composition sung to the sound of seven
      chords or tones. --Moore (Encyc. of Music).